A centrifugal fan includes a main plate rotatably driven by a fan motor, a shroud having an air inlet, and a plurality of blades provided between the main plate and the shroud. Conventionally, two-dimensional blades untwisted in a rotation axis direction have been mainly used as the blades of a centrifugal fan. Thus, the main plate and the blades have been integrally molded with resin. In recent years, however, it has become necessary to use three-dimensional blades having a shape twisted in a rotation axis direction for further reduction in the noise and power consumption of a centrifugal fan.
Patent Literature 1 describes an impeller of a centrifugal fan including a main plate made of resin, a plurality of hollow blades, and a side plate made of resin. Each of the hollow blades includes a resin first surface portion fixed to the main plate and a resin second surface portion attached to the first surface portion and forming a hollow space between the first surface portion and the second surface portion. With this impeller of a centrifugal fan, because the hollow blade includes the first surface portion and the second surface portion, the hollow structure of the blade is promoted to reduce the weight of the impeller even when the hollow blade is three-dimensional blade that extends in a twisted manner in an axis direction between the main plate and a side plate.